Story ends 17 chapters early?

Okay I got the Ultimate Edition on PC and I just beat it (or I'm pretty damn sure) if the last battle is Superman vs. Superman but when I won it said I unlocked chapter 33. Well I looked in the card thing when customizing my player card and there are card unlocks for up to chapter 50. So what the hell is up? I pressed "continue" when it booted me back into the menu and it just brought me to the beginning of the game so where are these mysterious 17 chapters I don't know about?

Those are LEVELS. You "Level up", like in an RPG. There's only chapters in the story for the non-DLC characters. So 10 chapters (10 characters).

You gain XP (experience points) by fighting (single player, local versus or online). You can use them to unlock stuff like costumes, cards and other fun stuff.

If you want more "story", play the regular Battle-mode (aka Arcade Mode), there's an ending for each character, but those are completely different from the main story and "non-canon" meaning they aren't technically what happened, just an alternate thing if for example The Joker won out of all the heroes/villains.